#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

int g_val = 100;

int main()
{
    pid_t id = fork();
    if(id == 0)
    {
        //child
        int flag = 0;
        while(1)
        {
            printf("我是子进程:%d, ppid: %d, g_val: %d, &g_val: %p\n\n", getpid(), getppid(), g_val, &g_val);
            sleep(1);
            flag++;
            if(flag == 5)
            {
                g_val=200;
                printf("我是子进程，全局数据我已经改了，用户你注意查看！\n");
            }
        }
    }
    else 
    {
        //parent
        while(1)
        {
            printf("我是父进程:%d, ppid: %d, g_val: %d, &g_val: %p\n\n", getpid(), getppid(), g_val, &g_val);
            sleep(2);
        }
    }
}

